Many modern storage systems include storage devices that store data on magnetic or optical storage media. For example, common hard disk drives include one or more disks and a disk controller to manage local operations concerning the disks and process instructions from systems using the disks. Analogous control architectures exist in optical storage media. The disks themselves in a hard disk drive (HDD) are usually made of an aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, two or more disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm). An actuator assembly supports a movable set of read/write heads for reading data from or writing data to the disks.
In normal operation, the head flies over the surface of the disk at a vertical height on the order of 2 millionths of an inch. The microscopic distance between the recording surface and the read/write head leaves little tolerance for vertical misalignment. Even very small angular misalignments of components resulting from vibration can cause the head to come in contact with the recording surface. Such physical contact may cause the head to generate contacts on the disk surface that may lead to a head-disk crash. This renders the disk inoperable and destroys any data stored on the recording surface. Likewise, horizontal misalignment due to vibration can throw a head off-track and cause delay while an actuator repositions to accommodate the change in alignment.
Disk drive components, such as fans, actuators for moving heads, and motors for turning disks, generate vibration and are subject to vibrations within their environment. Vibration-related problems are particularly acute as drives become increasingly compact and are used in multi-drive systems. As drives become more compact, tolerance for vibration-related misalignment decreases. As drives are used in multi-drive systems, the drives tend to be installed in proximity to each other, in arrays, such that vibrations created in a first disk can create adverse results in a second disk.
While embodiments are described herein by way of example for several embodiments and illustrative drawings, those skilled in the art will recognize that embodiments are not limited to the embodiments or drawings described. It should be understood, that the drawings and detailed description thereto are not intended to limit embodiments to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to.